Foundlings, I guess they could have been but they could have been reared by other family members if mother deceased.
Stories passed down may not be exactly right but there will be that 'grain of truth'. In this case perhaps just the wording.I can see one of the two perhaps. Even children of single mother's were recorded in Parish records but not politely (bastards) written in beside.
Children were often take by the government/church into orphanages een if the father was alive as it wasn't felt he could do a good enough job raising kids and working.
If the families circumstances weren't good they may have had other family members raise them you see a lot of that in Ireland.
I doubt there were any Irish travellers/gypsy's then but
I could be mistaken but I've never heard any reference to them before but you know that Mullingar and Athlone were densly populated by travellers.
Children whose parents had nothing went into Workhouses with their parents and the parents had to give up everything to be admitted. I think it more likely to be those horrible orphanages where children were treated as slaves by the nuns.
I looked up just in wiki pedia that the workhouse system started in ernest in 1834 after some new laws were enacted. Although in England a different format very similar was
started after the Black Death in 1631.
Speculating is all you can do sometimes looking into
Did you try the Irish Family History Foundation website yet? www.rootsireland.ie
Isabel is quite an unusual name for the times.A marriage record would give you both their father's names. A baptism has both mother and father's names
Athlone CofI 1810 only, deaths 1786-1875
Mullingar 1741-1900 with missing years 1747, 1820, 1822 and a note that father's were not always recorded on baptism records, nor witnesses. Marriages the years 1824-1833 are missing.
The average age of marriage 20-25 or 1839 approximately so you might be able to find the marriage. Usually marriages took place in the bride's parish but not always.
With both names John Sullivan and Isabella Hill you should be able to find any children they had born in Ireland.www.genealogy.nationalarchives.ie
Arthur Hill, Parish of Mullingar,Townland Petiswood
James Hill, St. Mary's Athlone Parish, TL Coorsan
There are 18 Sullivan's. Look at their children's names
to make a better guess as to the grandparents names.
Directories of Ireland show a number of Hill's from 1824-1894 but a few in 1824 & 1846, Mullingar and Atholone
you can see these free on www.failteromhat.com
Farmers don't start to show in the directories until 1881.
A couple might meet in a town setting rather than a church setting and be from different Parish's.
1854: Griffith Valuation
John Sullivan, Parish of Piercetown, Townland Rathcogue,
Poor Law Union Ballymahon, tenant of James Higgins
4a house and garden 1 acres 0 roods and 10 perches
This could be your John or his father if your John had left Ireland by 1854.
I'm going to look up a bit more about Irish Travellors, Gypsy's but not Romany Gypsy's. Although all Europes
gypsy's came out of India in the middle ages.
Apparently Irish travellers are ethnically Irish. In England they were called gypsy's but now travellers.